Four chambers — septum, valves, coronary arteries
Right atrium takes deoxygenated blood from the vena cava → right ventricle → pulmonary artery → lungs. Left atrium takes oxygenated blood from the pulmonary vein → left ventricle → aorta → body. The septum separates the two sides. AV valves sit between atrium and ventricle; semilunar valves at the base of the aorta and pulmonary artery. Coronary arteries branch off the aorta and supply the cardiac muscle itself.
Cardiac output = heart rate × stroke volume
Cardiac output () = heart rate (beats/min) × stroke volume ( per beat): 70 × 70 = 4900 at rest. Monitor heart rate by counting the pulse in a set time, or from an ECG trace. Physical activity raises heart rate — muscles need more oxygen and produce more . Adrenaline, from the adrenal glands, raises both heart rate and stroke volume.
(Extended) Thicker left ventricle, and CHD
The left ventricle pumps oxygenated blood to the whole body via the aorta — a greater distance at higher pressure — so its wall is thicker; the right ventricle only pumps to the lungs. Mark schemes want "whole body / greater distance / higher pressure", not "pumps harder". CHD risk factors: diet high in saturated fat, smoking, high blood pressure, physical inactivity. Prevention: low-fat high-fibre diet, no smoking, regular exercise, controlling blood pressure.
Drawn from real examiner reports.
Left ventricle sits on the diagram's right
A heart diagram is drawn as if the patient faces you, so the patient's LEFT ventricle appears on the diagram's RIGHT. Candidates label the diagram's left side "left ventricle" — that chamber is the right ventricle. Find the thicker wall, or trace the vessel: the left ventricle leads to the aorta, the right ventricle to the pulmonary artery.
Persistent across sittings: s23 Papers 12/13 Q19/Q20; s22 Papers 11/13/33 Q19 (s22; s23)
Semilunar valve ≠ atrioventricular valve
Asked to name the valve at the base of the aorta, the answer is semilunar valve. "Atrioventricular valve" is wrong — AV valves sit between atrium and ventricle — and "valve" on its own is not specific enough to score. Semilunar valves prevent backflow from the arteries into the ventricles when the ventricles relax.
Semi-lunar valve not named: s22 Paper 41 Q2a iii (s22)
The heart pumps — it does not transport
The heart pumps blood. "Transports blood" does not credit the mechanism — muscular contraction generating pressure — so it does not score. Use "pumps" in every description of heart function: the right side pumps deoxygenated blood to the lungs, the left side pumps oxygenated blood to the body.
Heart function described as "transport": s23 Paper 31 Q7a (s23)
Septum separates; valves stop backflow
The septum is a permanent muscular wall separating the left and right sides so oxygenated and deoxygenated blood do not mix. It does not prevent backflow — that is the job of the valves. Describing the septum as "stopping blood going the wrong way" describes a valve instead, and loses the mark.
Septum function confused with valves: w22 Paper 42 Q6a ii (w22)
"Measure the pulse" scores nothing
"Measure the pulse" and "feel the pulse" are both insufficient. The mark scheme wants the pulse counted in a set time (e.g. count for 15 seconds, then × 4), or an ECG used to measure heart rate. The pulse itself is the arterial wall expanding and recoiling as each heartbeat sends a pressure wave along the artery.
Pulse rate measurement insufficient: w22 Paper 33 Q6b (w22)
Coronary artery, not "cardiac artery"
The vessels supplying the heart muscle are the coronary arteries — "cardiac artery" is not an accepted term, and the pulmonary artery is a different vessel entirely (it carries deoxygenated blood to the lungs). Coronary arteries branch off the aorta just above the semilunar valve and run over the surface of the heart.
Coronary artery misidentified: w22 Papers 12/13/21 Q17/Q19; w22 Paper 42 Q6b i (w22)
Cardiac output: formula, then unit
Two marks: one for correct substitution, one for the answer with its unit. Write cardiac output = heart rate × stroke volume, substitute, multiply (never divide), and state . A resting answer near 5000 is plausible.
1 dm³ = 1000 cm³, not 100
If stroke volume is in but the answer is wanted in , divide the cardiac output by 1000. Rearrange the same formula when a value is missing: heart rate = cardiac output ÷ stroke volume; stroke volume = cardiac output ÷ heart rate.
Name the structure, then its action
For "describe the function of X", name the structure, use the precise action verb — separates (septum), prevents backflow (valves), supplies (coronary arteries), pumps (ventricles) — then state the consequence. "It helps the heart work" scores nothing.
Read heart rate off ECG peak spacing
An ECG records the heart's electrical activity as repeating peaks, one per beat. Read the rate from the spacing: widely spaced peaks mean a slower heart rate, closely spaced peaks a faster one. Comparison questions want that spacing stated explicitly.
The heart is a muscular organ that pumps blood around the body. It is located in the chest (thorax), slightly to the left of the midline, and is surrounded by the pericardium (a protective membrane).
Cardiac output (carbon dioxide = ; oxygen = ):
| Term | Definition | Typical resting value |
|---|---|---|
| Cardiac output | Total volume of blood pumped per minute | ~4900 cm³/min |
| Heart rate | Number of heartbeats per minute | ~70 beats/min |
| Stroke volume | Volume of blood pumped per beat | ~70 cm³ |
A person has a heart rate of 70 beats/min and a stroke volume of 70 cm³. Calculate the cardiac output in cm³/min.
(a) Name the four chambers of the heart. [2]
(b) State the function of the septum. [1]
(c) Name the blood vessel that:
